This invention relates to apparatuses for preventing the incorrect collating of signatures (hereinafter referred to as "incorrect collating preventing apparatuses" when applicable), and more particularly to an incorrect collating apparatus which automatically detects the incorrect collating of signatures which may be caused in gathering them by stacking one on another in the order of page numbers, and also the mixing of different grops of signatures, thereby to stop a signature gathering machine if necessary.
Heretofore, in a so-called signature gathering process for piling a plurality of signatures one on another in the order of page numbers into one book or magazine, the workers carry the signatures to a feeder box and piles them therein. For instance, in the case of one of the conventional saddle stitching machines, the signatures are loaded in the feeder box with the backs held downward, and a signature pulled out by the upper cylinder with its back held upward is opened and mounted on the gathering chain by means of the wraparound cylinder and the opening cylinder. If, in this case, some of the signatures are loaded upside down in the feeder box or unnecessary signatures are mixed in necessary signatures to be bound, it will lead to incorrect collating. Since the bookbinding operation should be carried out with great care and at high speed, the workers are liable to become fatigued as much. Accordingly, there has been a strong demand in the art for providing an apparatus which can automatically detect and prevent the incorrect collating of signatures.
Shown in FIG. 1 is a schematic diagram illustrating the aforementioned conventional saddle stitching machine to which this invention can be applied. Signatures 1 are loaded on the nose bracket 2a of a feeder box 2 with the backs held downward as shown in FIG. 2. These signatures loaded in the feeder box are depressed against a front plate 26 because the nose bracket 2a is tilted as shown in FIG. 1. The top signature 1A is sucked and retained by a vacuum sucker shifter 3, and is then clamped at its back by a clipper 4a provided on an upper cylinder 4. The signature thus clamped is moved in the direction of the arrow as the cylinder 4 rotates. When the back 1a is abutted against a printing guide 5 one wing of the signature 1 is clamped by a clipper 6a of a wraparound cylinder 6, while the other wing is clamped by a clipper 7a of an opening cylinder 7. Then, as these two cylinders 6 and 7 are rotated in the opposite directions as indicated by the arrows, the signature is allowed to leave the clamps 6a and 7a, and it is mounted over a gathering chain 9 with the aid of the pressure of air jetted by air-purge nozzles 8.
A conventional incorrect collating preventing apparatus comprises a photoelectric detector assembly which operates to photoelectrically detect marks 1b printed on signatures by the utilization of light reflected thereby.
The conventional photoelectric detector assembly, as shown in FIG. 3A, comprises: a light source 31 such as an ordinary electric lamp; a condenser lens 33 provided on the optical axis 32 of the light source 31, for changing light beams from the light source 31 into parallel light beams; a half mirror 35 adapted to reflect the parallel light beams in a direction of an optical axis 34 perpendicular to the optical axis 32; and a focusing lens 87 adapted to focus the light beam thus reflected into a light spot about 5mm in diameter on a surface 36 to be detected. Light beams reflected by the surface 36 are applied to a light receiving element 39 through the focusing lens 37, the half mirror 35, and a focusing lens 38 provided on the optical axis 34. When the surface 36 is moved, being irradiated by the light spot, variations in intensity of the reflected light beams are converted by the photoelectric element 39 into electrical signals which are utilized for detection.
However, this conventional photoelectric detector assembly is disadvantageous in the following points: If it is assumed that the transmission factor and reflection factor of the half mirror are respectively 50% and 50%, when the light beams from the light source are reflected toward the surface to be detected by the half mirror, the intensity thereof is reduced as much as 50%, and when the light beams reflected by the surface passes through the half mirror, the intensity thereof is reduced 50%. Accordingly, the light receiving element 39 cannot receive light satisfactorily high in intensity without increasing the intensity in brightness of the light source, which results in an increase in power consumption and a reduced service life of the assembly. Furthermore, out of the light beams reflected by the half mirror, the light beams adjacent the optical axes are further reflected by the surface of the focusing lens 37 and are applied, as stray light beams, to the photoelectric element 39. Therefore, the photoelectric element 39 is brought into so-called biased state, as a result of which the difference in intensity between the light reflected by a portion of the surface to be detected where the printed mark is provided and the light reflected by a portion of the same where no printed mark is provided, is reduced. This is undesirable from the point of view of preventing incorrect collating.
Furthermore, in the conventional incorrect collating preventing apparatus the photoelectric detector assembly has only one optical system for detection. The assembly is first set on the portions of signatures where nothing is printed, thereby to produce and store a reference signal, and then it is set on printed marks provided on the signatures thereby to produce a printed mark signal. Then, the printed mark signal is compared with the reference signal thereby to determine the signature loading conditions.
Accordingly, whenever a different group of books or magazines are bound, that is, the quality of paper is changed, or whenever, even if the quality of paper is unchanged, its color is changed, adjustment is required, which leads to a difficulty in maintenance.
In addition, as only one photoelectric element is employed in the photoelectric detector assembly, the effects of the initial drift and temperature drift os the photoelectric element cannot be disregarded. Accordingly, the apparatus cannot be used until such drifts become stabilized, which results in the waste of time. Furthermore, in the case where the distances between the photoelectric detector assembly and the sides of the signatures are caused to be non-uniform by irregularly disposing the signatures on the feeder box, or in the case where the printed marks have become deteriorated in density, erroneous operations may take place.